Boosted Photocatalytic Activities of Ag2CrO4 through Eu3+-Doping Process

Ag2CrO4 is a representative member of a family of Ag-containing semiconductors with highly efficient visible-light-driven responsive photocatalysts. The doping process with Eu3+ is known to effectively tune their properties, thus opening opportunities for investigations and application. Here, we report the enhancement of the photocatalytic activity and stability of Ag2CrO4 by introducing Eu3+cations. The structural, electronic, and photocatalytic properties of Ag2CrO4:xEu3+ (x = 0, 0.25, 0.5, 1%) synthesized using the coprecipitation method were systematically discussed, and their photodegradation activity against rhodamine B (RhB), ciprofloxacin hydrochloride monohydrate (CIP), and 4-nitrophenol (4-NP) was evaluated. Structural analyses reveal a short-range symmetry breaking in the Ag2CrO4 lattice after Eu3+ doping, influencing the material morphology, size, and electronic properties. XPS analysis confirmed the incorporation of Eu3+ and alteration of the surface oxygen species. Furthermore, photoluminescence measurements indicated that the doping process was responsible for reducing recombination processes. The sample doped with 0.25% Eu3+ exhibited superior photocatalytic performance compared to pure Ag2CrO4. Scavenger experiments revealed an increase in the degradation via •OH reactive species for the sample doped with 0.25% Eu3+. DFT calculations provided atomic-scale insights into the structural and electronic changes induced by the Eu3+ doping process in the Ag2CrO4 host lattice. This study confirms that Eu3+ doping alters the band structure, enabling different degradation paths and boosting the separation/transfer of photogenerated charges, thereby improving the overall photocatalytic performance.

Based on the three models showed in Figure S7, the values of E were calculated and compared.An analysis of the E values render that that the substitution in the octahedral coordination site is energetically favored over the tetrahedral one at 3.12% and at 6.25% (by 0.84 eV and 1.89 eV, respectively), being the stability order (1)>( 3)>( 2) , as can be seen in Table S4.

Figure S7 .
Figure S7.Representation of the three Eu 3+ doping Ag 2 CrO 4 systems simulated in this study.The gray polyhedra indicate the [AgO 6 ] substitution site, the green ones the [AgO 4 ] substitution site and the dotted yellow circles indicated the position of V Ag formation.

Figure S8 .
Figure S8.Illustration of the local coordination of the Eu 3+ doped site in the Ag 2 CrO 4 model system (3): [EuO 6 ] formation for substitution in 4a site and the [EuO 7 ] and [AgO 5 ]for substitution in 4c site.

Table S2 .
Reported values of the lattice parameters of Ag 2 CrO 4 (Crystal Structure Database (ICSD).calculated for a 12.5% of Eu 3+ doping, which is much higher than the experimental value of 1%.Theoretical Raman spectra of Ag 2 CrO 4 and Eu 3+ -doped Ag 2 CrO 4 (resulting in a Eu 3+ doping percentage of 12.5%).
We have calculated the Raman spectra of Ag 2 CrO 4 in a single, in which the Eu3+doping percentage is 12.5 %.The calculated Raman spectra of Ag 2 CrO 4 unit cell are displayed in FigureS2.Two intense A g modes, associated to the symmetrical stretching 3+ occupation.As result of the Eu 3+ substitution, the most intense band (858 cm -1 ) shifts to lower energy.In the spectra of the 4a site Eu-doped Ag 2 CrO 4 two weak A g modes are observed at 222 and 234 cm -1 corresponding to the stretching of Ag-O and Eu-O bonds (B 1g mode in pure Ag 2 CrO 4 ).Additional contribution is observed regarding to Eu-O-Cr stretching and Cr-O-Ag bending at 263 cm -1 .Lowintensity bands, assigned to symmetrical and asymmetrical bending modes, Cr-O-Eu bending, in the region between 352 and 439 cm -1 are found.O and Eu-O bonds.Additional contribution is observed regarding to Eu-O-Cr stretching and Cr-O-Ag bending at 328 cm -1 and low-intensity bands, associated to symmetrical and asymmetrical bending modes of Cr-O-Eu, are found in the region between 353 and spectra has

Table S3 .
FWHM values obtained from the Raman band located at 807 cm -1 for the assynthesized samples.